<!DOCTYPE html>
<title>Tests scrolling with anchor in fixed-positioned scroller</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#scroll">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/test-common.js"></script>

<style>
body {
  margin: 0;
  height: 200vh;
}

#scroller {
  position: fixed;
  width: 200px;
  height: 200px;
  overflow-y: scroll;
}

#anchor {
  position: absolute;
  width: 100px;
  height: 100px;
  top: 200px;
  background: orange;
  anchor-name: --a;
}

#target {
  position: fixed;
  width: 100px;
  height: 100px;
  bottom: anchor(top);
  position-anchor: --a;
  background: lime;
}
</style>

<div id=scroller>
  <div id=anchor></div>
</div>
<div id=target></div>

<script>
promise_test(async () => {
  await waitUntilNextAnimationFrame();
  assert_equals(target.getBoundingClientRect().top, 100);

  document.documentElement.scrollTop = 100;
  await waitUntilNextAnimationFrame();
  assert_equals(target.getBoundingClientRect().top, 100);
}, 'Target should not scroll with viewport when anchor is in fixed-positioned scroller');
</script>
